Excitation Process Research Articles

Determination of alkali metal elements in solid biomass fuel by laser-induced breakdown spectroscopy: Analysis and reduction of chemical matrix effects.

Rapid and accurate detection of the biomass potassium (K) content in biomass is crucial for mitigating ash deposition and fouling issues in biomass fuel combustion processes. Laser-induced breakdown spectroscopy (LIBS) offers a promising approach for rapid analysis of biomass elemental. However, the accuracy of LIBS detection is susceptible to chemical matrix effects. Particularly in the case of biomass, characterized by its complex composition, the absence of pertinent studies on effect mechanisms impedes the enhancement of analytical accuracy. In this study, we investigated and compared two types of matrix effects related to chemical properties in biomass samples (analyte forms and matrix composition). Firstly, the inconsistency of K spectral response among different chemical properties samples and the performance of univariate models were analyzed. The results indicate that, compared to the chemical forms, differences in composition are the dominant factor of chemical matrix effects. Moreover, the compositional content of biomass samples is analyzed to correlate the matrix effect in LIBS measurements to a chemical property of the specimen. It is indicated that differences in volatile and ash content may lead to variations in the plasma excitation process, resulting in distinct spectra. Finally, a knowledge-based regression approach was employed to attenuate chemical matrix effects, the main influencing factors identified were analyzed as a priori knowledge for variable selection and inputting them into a partial least squares model. And 13 real solid biomass fuels were measured, resulting in root mean square error of prediction (RMSEP), R2, and average standard deviation (ASD) of 0.99, 0.050%, and 0.001%, respectively. This study investigated the influence of matrix effects related to biomass chemical properties on LIBS measurements, achieving rapid measurement of K. It promotes the application of LIBS in solid fuels and provides a methodological reference for LIBS analysis of complex matrix materials.

Numerical simulation method for generating seismic waves by a simplified point source based on seismic-while-excavation in coal mine roadways

The advanced geological prediction of seismic-while-excavation (SWE) in coal mine roadways employs the noise vibrations generated during the construction process as the signal source. The excitation process of seismic waves derived from this noise source significantly differs from that associated with conventional pulse sources. Exploration of the characteristics and process involved in exciting seismic waves through excavation noise sources is undertaken. Initially, challenges posed by complex vibration sources during excavation are addressed, with analysis of signal characteristics derived from field data and consideration of the excavation environment. Investigation of the seismic wave excitation forms of these complex noise sources leads to a summary of their characteristics. The simplification of various excavation machinery into distinct forms of point sources facilitates theoretical analysis. Coupling the excitation processes of each point source and leading into virtual source theory of seismic record interferometry reconstruction results in a simplified point source time function of excavation noise sources. Analysis of the types and magnitudes of forces exerted by the cutting head during coal seam excavation, in conjunction with the operating mode of a boom-type roadheader, is conducted. A spatial loading method for the noise source is proposed, grounded in the components of the excited wavefield. The staggered grid finite difference algorithm is employed for numerical simulations. Comparison of synthetic seismic records with field-measured data validate the rationality and effectiveness of the simulated source term. A theoretical foundation for future investigations into the imaging and inversion of excavation noise sources is established.

Fast plasma production by intense femtosecond extreme ultraviolet and x-ray pulses

We develop a semiempirical model to describe the creation of an electron plasma in matter at extreme conditions, as excited by high-intensity, extreme ultraviolet (EUV) or x-ray radiation pulses currently available at free-electron laser (FEL) facilities. In typical FEL experiments, EUV and x-ray pulses are used to investigate highly excited states of matter produced by optical pump pulses. The pump pulses, promoting electrons from delocalized valence band states, excite the system often through multiphoton absorption processes and/or shock wave propagation. Instead, the use of FEL radiation as a pump allows triggering electron transitions from bound, core states to nearly free levels above the Fermi energy, promptly generating a highly excited state, toward the warm dense matter regime. We model such an excitation process starting from the optical properties of the analyzed materials and first-principle considerations, with the aim of motivating further studies in this scheme. We apply our model to predict the differences in the plasma creation process in insulators and metals, at varying exciting pulse wavelength and fluence, and we interpret the results in terms of the different nature of the investigated systems. Furthermore, we explore the effect of the finite core hole lifetime on the plasma formation and relaxation dynamics. We show the model is suited for the interpretation of real experimental data obtained from a prototypical insulating crystal (LiF) in a EUV FEL pump–optical transmission probe experiment. Published by the American Physical Society 2025

Optical conductivity of the topologically nontrivial MXenes Mo2HfC2O2 and W2HfC2O2 : First-principles calculation and effective model analysis

The optical conductivity and the relevant electronic excitation processes are investigated in topologically nontrivial MXenes Mo2HfC2O2 and W2HfC2O2 utilizing first-principles calculation and effective model analysis. The numerical calculation based on the first-principles band structure reveals the presence of several characteristic features in the spectrum of optical conductivity as a function of photon energy. The drastic dependence on the photon polarization angle is also presented in terms of apparent features. In this paper, an effective model is also generated referring to the crystal symmetries and applied to reveal the microscopic origin of the characteristics. Then, it is shown that some features are strongly related to parity inversion between the conduction and valence bands, the key signature in electronic structures of topologically nontrivial insulators. Published by the American Physical Society 2025

Oscillatory mechanoluminescence of Mn2+-doped SrZnOS in dynamic response to rapid compression

Photon emission may be continuously produced from mechanical work through self-recoverable mechanoluminescence (ML). Significant progress has been made in high-performance ML materials in the past decades, but the rate-dependent ML kinetics remains poorly understood. Here, we have conducted systematic studies on the self-recoverable ML of Mn2+-doped SrZnOS (SrZnOS: Mn2+) under rapid compression up to ~10 GPa. Rate-dependent distinct kinetics is revealed: a diffuse-like ML behavior below ~1.2 GPa/s, oscillatory emission with a series of ML peaks at critical rate of ~1.2–1.5 GPa/s, and suppression of ML above 1.5 GPa/s. Analysis from the rate-independent structural evolution and photoluminescence under high pressures show that the oscillatory ML emission at the critical rate corresponds to multi-cyclic piezoelectrically-induced excitation (PIE) and self-recoverable processes. Both characteristic time (τ) for the PIE and self-recoverable processes are minimized at the critical rate, indicating the time limit of ML in the dynamic response to rapid compression. High temperature is slightly favorable for PIE, but is unfavorable for the self-recoverable process. The present work uncovers the temporal characteristics of self-recoverable ML and provides insight into understanding the rate-dependent ML kinetics in the mechanical-photon energy conversion, conducive to the design of ML-based optoelectronic devices.

Fully relativistic distorted-wave method for collision excitation process between electron and atom

The electron-atom (ion) collision excitation process is one of the most common inelastic scattering processes. It is of great significant in the fields of astrophysics and laboratory plasma. The relativistic distorted-wave method is a widely used theoretical tool for studying electron-atom (ion) collisions, with the aim of obtaining scattering parameters, such as impact cross sections and rate coefficients.<br>In recent years, we have developed a set of fully relativistic distorted-wave methods and programs for studying the electron-atom collision excitation processes. This method is based on the multi-configuration Dirac-Hartree-Fock (MCDHF) method, along with the corresponding packages GRASP 92/2K/2018 and RATIP. The present paper introduces the calculations of continuum state wave functions, total and differential cross sections, state multipoles, integral and differential Stokes parameters of the radiation photon following the impact excitation processes of polarized electrons and atoms. The influence of electron correlation effects, Breit interaction, and plasma screening effects on the excitation cross sections is discussed. The present methods and programs offer several advantages:<br>(1) In the calculations of the continuum electron wave functions, the direct and exchange interactions between the bound electron and the continuum electron are included. Then, the anti-symmetrized coupling wave functions, which is composed of the continuum electron and the ion wave functions, are utilized as the wave function of the system. This method has been employed to study the low to high energy electron scattering processes.<br>(2) In this method, the target state wave function is obtained using the MCDHF theory and the corresponding GRASP packages. The MCDHF method has the advantage of being able to consider the electron correlation effects, including valence-valence, core-valence, and core-core correlations, as well as the Breit interaction and quantum electrodynamics (QED) effects effect on the target state wave function. Furthermore, the calculation of the collision excitation matrix elements also incorporates the contribution of the Breit interaction. Consequently, the present method combines the advantages of both the MCDHF method and distorted-wave method, making it suitable for studying the scattering processes of highly charged ions. In addition, it facilitates the study of the influence of higher-order effects on the collision dynamics, thereby enabling the obtaining high-precision theoretical data.<br>(3) The current method and program can also be utilized to study the scattering cross section of electron-atom collision excitation processes, as well as the impact of plasma screening effects on collision excitation. Furthermore, the state multipoles, differential Stokes parameters, integral Stokes parameters and orientation parameters of electron-complex atom collision excitation can be studied in detail using the present method and program.

Influence of point defects on laser-induced excitation in silicon

We studied the influence of defect states on the laser excitation process in silicon using time-dependent density functional theory. We assumed two types of point defects: interstitial oxygen and silicon vacancies. We found that the photoabsorption efficiency increased with defect density in both cases owing to the color center. These defects distorted the crystal structure, thereby relaxing the selection rules and changing the indirect gap to direct. At low laser intensities, the defect states dominated the absorption process. However, as the laser intensity increased, the excitation efficiency approached that of crystalline silicon. In addition, we observed that the excitation efficiency did not scale linearly with the pulse length. Notably, in the case of Si vacancies, saturable absorption reduced photoabsorption significantly. Our results suggest that the existence of a defect induces the even-order high-harmonics generation. The enhancement of even-order high-harmonics generation by the silicon vacancy is larger than the interstitial oxygen. Published by the American Physical Society 2024

Enhanced and directional fluorescence emission regulated by dual resonant surface modes

Fluorescence emission regulation is of great interest for its promising applications in various fields such as microscopy, chemical analysis, encryption, and sensing. Most studies focus on the regulation of the fluorescence emission process. However, the spectral separation of excitation and emission of fluorophores requires careful design of resonances to cover both emission and excitation wavelengths, which is a better choice to enhance fluorescence intensity. In this Letter, we engineer an efficient dielectric concentric ring grating on a dielectric multilayer film with two resonate modes to enhance the excitation and emission processes. By careful design of the structure, the two resonate modes occupy similar in-plane wave vector and overlap in the fluorescence area. Experimentally, fluorescence intensity enhancement about five times and the divergence of fluorescence into free space compressed to less than 5° are achieved. Our work provides what we believe to be a new strategy for the realization of high directional on-chip light emitter at room temperature.

Effect of pressure and current density on metastable argon dynamics in low-pressure Ar-O2 plasma

Abstract Non-thermal plasma demonstrates a significant enhancement in efficiency when oxygen is added into the plasma mixture, particularly in processes such as thin-film oxide deposition, poly film removal, and photoresist mask ashing. This study examines the behavior of metastable argon states (1s5 and 1s3) in Ar-O2 mixture plasma, generated by a 50 Hz pulsed DC power supply under low-pressure conditions ranging from 1 mbar to 7 mbar. The densities of metastable argon states were assessed at varying conditions of current density, argon concentration, and filling gas pressure, utilizing optical emission spectroscopy (OES). The argon emission line ratio technique was employed to determine the plasma parameters. Experimental results indicate that electron density increases with current density, driven by enhanced excitation and ionization processes, while higher argon concentrations facilitate efficient ionization. The declining trend of the electron density with an increase in filling gas pressure is attributed to higher-pressure collisional processes. Metastable argon atoms exhibit heightened density with increased current density and argon percentage but decrease with elevated pressure due to loss processes. The regulation of metastable states is crucial for processes like etching, surface modification, and sterilization, providing a crucial step to the optimization and enhancing these applications.

Direct Implementation of MSn Using Frequency Scanning Collision Induced Dissociation in a Digital Ion Trap Mass Spectrometer.

Tandem mass spectrometry (MSn) is one of the most effective methods to obtain the structures of organic molecules, enabling the observation of multigenerational ion fragments. Collision-induced dissociation (CID) is currently the most mature technique for mass spectrometry analysis. Ion trap mass spectrometry (ITMS) is favored for on-site detection field, due to its ability of MSn analysis with a single trap and its small size. However, conventional MSn analysis in ITMS requires repeated isolation and excitation processes multiple times, causing high complexity of the entire scanning process. Additionally, the fragment ion detection in ITMS is limited by low-mass cutoff (LMCO) and the weak fragmentation yield. In this study, a method named reverse scanning-collision induced dissociation (RS-CID) is proposed, which involves increasing RF and AC frequencies while maintaining RF voltage constant during the CID process. Twelve representative illegal drugs were analyzed adopting this method, enhancing the intensities of low-mass fragment ions compared to conventional dissociation method. Moreover, experimental results with ketamine and methamphetamine show that RS-CID effectively reduces the LMCO effect and slightly improves CID efficiency. It also enables direct acquisition of their multigeneration fragment ions spectra in a single sequence of ion injection, cooling, isolation, RS-CID, cooling, mass scanning and empty. The experiments to distinguish between the isomers ab-4en-pinaca and adb-3en-butinaca as well as the isomeric compounds 5f-cumyl-pegaclone and cumyl-pipetinaca were also successful by this method. In summary, RS-CID enables MSn analysis in a single sequence and improves the low-mass fragment ions intensity. It can simplify workflows, achieve faster analysis and provide more valuable mass spectral information.

Multifunctional SERS Chip for Biological Application Realized by Double Fano Resonance.

The in situ and label-free detection of molecular information in biological cells has always been a challenging problem due to the weak Raman signal of biological molecules. The use of various resonance nanostructures has significantly advanced Surface-enhanced Raman spectroscopy (SERS) in signal enhancement in recent years. However, biological cells are often immersed in different formulations of culture medium with varying refractive indexes and are highly sensitive to the temperature of the microenvironment. This necessitates that SERS meets the requirements of refractive index insensitivity, low thermal damage, broadband enhancement, and other needs in addition to signal enhancement. Here, we propose a SERS chip with integrated dual Fano resonance and the corresponding analytical model. This model can be used to quickly lock the parameters and then analyze the performance of the dual resonance SERS chip. The simulation and experimental characterization results demonstrate that the integrated dual Fano resonances have the ability for independent broadband tuning. This capability enhances both the excitation and radiation processes of Raman signals simultaneously, ensuring that the resonance at the excitation wavelength is not affected by the culture medium (the refractive index) and reduces heat generation. Furthermore, the dual Fano resonance modes can synergize with each other to greatly enhance both the amplitude and enhanced range of the Raman signal, providing a stable, reliable, and comprehensive detection tool and strategy for fingerprint signal detection of bioactive samples.

Synthesis and Excited State Proton Transfer (ESPT) Studies of 2-(6-Substitutedbenzo[d]Thiazol-2-Yl)Naphthalen-1-Ol Derivatives.

This study reports the rapid intramolecular proton transfer studies upon photo excitation of 2-(benzo[d]thiazol-2-yl)naphthalene-1-ol derivatives, yielding tautomer emission with large Stokes shift. Employing photophysical studies, density functional theory (DFT) and, time-dependent density functional theory (TD-DFT) methods, we scrutinize excited state intramolecular proton transfer (ESIPT) modulation over varying solvent polarities. Analysis of UV-Visible and fluorescence spectra, alongside exploration of hydrogen bond dynamics, reveals solvation effects on the excited state proton transfer process. Theoretical vibrational spectra confirm enhanced hydrogen bond strength in the excited state which is sensitive to the solvent polarity. Energy profile curves and the scatter graph depict impact of solvent polarity on ESIPT. Additionally, molecular interactions and X-ray diffraction studies of the title compound 4a are presented.

Exploring the dynamics of H atom guested endofullerene embedded in plasma with ultrashort chirped laser pulses

In this work, the effects of an ultrashort laser pulse on the excitation and ionization dynamics of a hydrogen guested endofullerene system embedded in a quantum plasma environment under spherical encompassment are investigated. The interaction of the plasma environment is considered within the more general exponential cosine screened Coulomb (MGECSC) potential model, and the excitation and ionization dynamics are analyzed through plasma screening parameters. For endohedral confinement, the relevant model that aligns with experimental data and is most suitable for static endohedral encapsulation is the Woods–Saxon potential model. By considering different numerical ranges of the parameters in this model, the effects of various forms of fullerenes are thoroughly explained through the analysis of confinement depth, spherical shell thickness, inner radius and the smoothing parameters. The effects of the characteristic properties of the laser pulse, such as its intensity and frequency, on the probability dynamics are also discussed. All parameters and their respective ranges are important for optimizing system performance. Additionally, the alternatives of all parameters related to the plasma-embedded endofullerene system for probability dynamics are considered. In this context, the findings cause new ideas in the controlled excitation and ionization processes of endofullerene systems embedded in a quantum plasma environment and provide a significant foundation for future experimental studies.

Search for QCD axion dark matter with transmon qubits and quantum circuit

We propose a direct axion dark matter (DM) search using superconducting transmon quantum bits (qubits) as quantum sensors. With an external magnetic field applied, axion DM generates an oscillating electric field, which causes the excitation of the qubit. Such an excitation can be regarded as a signal of the axion DM. We provide a theoretical consideration of the excitation process of the qubits, taking into account the effects of the shielding cavity surrounding the qubits, and estimate the signal rate for the axion DM detection. We also discuss the enhancement of the DM signal by using cavity resonance and entangled quantum sensors realized by a quantum circuit. Combining these two effects, we can reach the parameter region suggested by QCD axion models. Published by the American Physical Society 2024

Measurements of Minor Loop Position and Shape Depending on Inductor Excitation Process

Measurements of Minor Loop Position and Shape Depending on Inductor Excitation Process

Understanding the Excited Properties and the Luminescence Mechanisms of ns2 Type Ion Doped Phosphors: A First-Principles Study

Luminescent materials doped with ns2-type ions, such as Bi3+, Sb3+ ions, exhibit several excited states that can provide optical transitions, including the optical transitions within the electronic configuration of ns2 ions, the valence band to ns2 ions charge transfer (CT) transitions, the metal-to-metal charge transfer (MMCT) transition between the ns2 ions and the conduction band, and the intervalence charge transition (IVCT) between the dopant pair. The luminescence properties of these materials are significantly influenced by the environment, making the ns2 ions excellent activators for phosphors. Our talk will present the first-principles studies that revealed the geometric and electronic structures of the ground and excited states of ns2 ions, constructed the configuration coordinate diagrams, and analyzed the dynamic processes of excitation, relaxation, and emission. We will also briefly present some work on ns2 ions doped phosphors studied by the combination of first-principles and experimental methods, demonstrating the importance of theoretical calculations for the design and performance improvement of novel luminescent materials. Figure 1

Photoacoustic and plasmaelastic waves propagation in semiconductor medium heated by pulsed excitation with magnetic field effect

Semiconductor materials play a crucial role in the fields of science, engineering, and technology due to their high importance. In this work, photoelastic (PE) deformations due to the photonically excited processes are studied according to the photogenerated carriers (plasma waves) during the recombination processes. A photoacoustic theoretical model for the optically excited Silicon (Si) polymer material under the effect of magnetic field is introduced. The coupled between the acoustic and plasm-thermomechanical waves is considered. The governing equation according to the photo-thermoelasticity theory with acoustic pressure is derived. The optoelectronic and thermoelastic properties of semiconductor material are taken into account. The analytical expression of the main physical fields (temperature, mechanical stress, displacement, carrier density, and acoustic pressure) is obtained mathematically using the harmonic wave technique. The theoretical results are represented graphically due to the strength of the magnetic field in two and three dimensions (2D and 3D) and some comparisons are investigated.

L-Cysteine-Modified Carbon Dots Derived from Hibiscus rosa-sinensis for Thiram Pesticides Identification on Edible Perilla Leaves.

In this work, environmentally friendly fluorescent carbon dots (C-dots) were developed for the purpose of thiram identification in the leaves of perilla plants. Powdered plant petals from Hibiscus rosa-sinensis were hydrothermally combined to create C-dots. Analytical techniques, such as scanning electron microscopy, energy dispersive X-ray spectroscopy, high resolution transmission electron microscopy, Raman spectroscopy, ultraviolet spectroscopy, Fourier transmission infrared spectroscopy, and photoluminescence were employed to examine the properties of C-dots. To enhance their functionality, an l-cysteine dopant was added to the C-dots. Since this process produces highly soluble C-dots in water, it is simple, inexpensive, and safe. The excitation process and the size of the blue luminescent C-dots both affect their photoluminescent activity. Furthermore, thiram in aqueous solutions was effectively identified by using the generated C-dots. Additionally, the ImageJ program was used to measure the colors red, green, and blue. High-resolution TEM (HR-TEM) revealed that the l-cysteine-doped carbon dots had an average particle size of 2.208 nm. Additionally, the lattice fringes observed in the HRTEM image showed a d-spacing of around 0.285 nm, which nearly corresponds to the (100) lattice plane of graphitic carbon. A Raman spectrum study was also performed to investigate the relationship between carbon dots and pesticides in the actual samples. In the end, thiram levels in perilla leaves with nondoped and doped C-dots could be distinguished with 100% accuracy using the constructed partial least-squares discriminant analysis machine learning model. The information gathered therefore demonstrated that the synthetic C-dots successfully and efficiently provide rapid and sensitive detection of hazardous pesticides in edible plant products.

Three luminescent Zn/Cd-based MOFs for detecting antibiotics/nitroaromatic compounds and quenching mechanisms study

Precise control of experimental conditions is essential for synthesizing metal-organic frameworks (MOFs) to enable multi-functional detection of antibiotics and nitroaromatic compounds. In this study, three MOFs (Zn-CIP-1, Zn-CIP-2 and Cd-CIP-3) were synthesized using 5-(4-cyanobenzyl)isophthalic acid (5-H2CIP) and 4′-(4′'-pyridyl)-2,4′:6′,4′'-terpyridine ligands (pyterpy) under varying hydrothermal synthesis conditions. Zn-CIP-1 ([Zn(CIP)(pyterpy)]·2H2O) exhibits a two-dimensional layered skeleton structure, while Zn-CIP-2 ([Zn3(CIP)3(pyterpy)2·1·5H2O] and Cd-CIP-3 ([Cd3(CIP)3(pyterpy)2]) are isomorphic crystals with three-dimensional topological structures. Zn-CIP-1 selectively detects metronidazole (MET) and Zn-CIP-2 detects ornidazole (ORN) in aqueous solutions. Cd-CIP-3 exhibits significant fluorescence quenching with MET or ORN. These MOFs can also detect nitrobenzene (NB) in aqueous solutions with different quenching percentages. Experiments and density functional theory reveal that the main quenching mechanism of Zn-CIP-2 includes static/dynamic quenching, competitive absorption, and photo-induced electron transfer. The analysis of weak interactions, electron excitation, and emission processes demonstrates the important role of π-π stacking interactions in electron transfer processes. This study offers insights into the development of multi-functional fluorescent sensors.

Determination of grout compactness in rebar grouted splice sleeves using frequency domain characteristics of the excitation process

Grouted splice sleeves are widely used in assembly building connections. However, void defects within the sleeve directly affect the load-bearing capacity of the building structure. This paper presents a new method for detecting void defects inside a grouted splice sleeve based on the frequency domain characteristics of mechanical vibration waves. This method analyszes the grouted spliced casing containing void defects as a gas-liquid two-phase flow system. To confirm the validity of the method, this paper builds a test setup for testing. The results showed that the test method can effectively detect the void defects and the volume of the defects inside the grouted splice sleeves when the grout is not solidified.